There exist various industrial processes that utilize substantial quantities of catalysts and/or sorbents in order to manufacture different products. For example, one of the largest consumers of catalysts and sorbents is the oil refining industry, which utilizes catalysts/sorbents in different processes, such as the fluid catalytic cracking (FCC) process, the hydrotreating process, the hydrocracking process, and the process of the sorption of sulfur oxides from flue gas, among others. Other industrial processes utilizing catalysts and/or sorbents in other industries include the fertilizer industry, the chemicals sector, and the automotive industry (such as in catalytic converters).
Within these industrial processes that use catalyst and/or sorbent materials, many are based upon utilizing aluminum-containing compounds as part of the catalyst/sorbent. Additionally, many also contain aluminum or non-aluminum containing molecular sieve materials as part of the catalyst/sorbent. For example, in the FCC process and in the hydrocracking process, the molecular sieve is a zeolite. More specifically, it is a zeolite of the Y-type or the faujasite-type.
Some industrial processes utilize catalyst/sorbents on a periodic basis, meaning that catalyst/sorbent material is loaded into vessels/columns and is run with little or no change over long periods of time. In other processes, fresh catalyst/sorbent material is periodically or continuously added in order to account for reductions in performance and/or activity due to physical losses, or deactivation due to factors such as steam, temperature, time and contaminant metals contained in the feedstock. One example of such a process requiring replacement or replenishment of the catalyst/sorbent material is the FCC process.
To the extent additions of fresh catalyst exceed the physical losses of the processing unit, there is a need for further withdrawal of spent catalyst from the unit. Such spent catalyst can no longer function properly in the process due to the deposition of sulfur, carbon, vanadium and/or other elements which inhibit or diminish the catalytic activity. This type of material is often referred to as either spent catalyst, equilibrium catalyst, or simply as “ECAT.” Typical withdrawals from the FCC process range from a few tons per day, to as much as thirty, or more, tons per day. The methods of disposing of this spent material vary depending on the quality of the material. For instance, material which is low in contaminant metals, and most likely high in remnant activity, is often resold and incorporated in full, or more typically, as a supplement to the new, or fresh, catalyst being added to another FCC unit. The spent catalyst may also be used during unit upset conditions, start-up of the process following a shutdown due to new unit installation, maintenance, or other planned or unplanned shutdowns. Spent catalyst that is not capable of suitable performance in another refinery is often disposed of in landfills, or by incorporating it into other industrial processes/products such as by incorporating it into cement and road pavement. Alternatively, the spent catalyst may have other catalytic uses in other processes that require a particular property of the spent material, such as surface area/sites, or heavy molecule processing capability.
At present, most catalyst is not considered to be hazardous waste, so the presence of the various metals contained in the catalyst are not a hindrance to normal disposal in landfills. It is possible that in the future, government entities in various countries around the world may impose regulations that would limit the disposal options, and/or that would add a significant economic cost to the disposal operation.
Instead of simple disposal of the entire spent catalyst in landfills, some catalysts that contain expensive or hazardous components can have those components recovered prior to disposal. Often, the entire catalyst is dissolved in order to recover the metals, and then the final solid residue is made environmentally safe for disposal prior to such disposal. One example of this type of material is a hydrotreating catalyst, which often contains metals such as Cr and Mo. Other type of catalysts subject to recovery may contain large amounts of precious metals (i.e., platinum, palladium, etc.), which are valuable.
Improvement of the performance of spent catalyst has also been of great interest. The goal is typically to either separate high performing catalyst from low activity catalyst, or to improve the activity of the bulk catalyst. This has been known to be performed using either magnetic separation or chemical treatment processing of the spent catalyst. However such processes are not routinely utilized upon the bulk of spent catalyst. The main reason is believed to be that the performance improvement per unit cost has not been high enough, when compared to simply purchasing new catalyst.
There remains a need to find new processes which are capable of economically increasing the performance of spent catalyst, and/or in recovering metals contained in the catalyst prior to disposal, especially in recovering rare earth materials, which are becoming increasingly expensive. Some of the objectives of the present invention are to address these needs, among others, with novel compositions and processes, which processes can also be applied to sorbents.